The science of pharmaceutical chemistry has progressively provided more and more specific and potent drugs for the treatment and prevention of illness. However, until quite recently, there has been no means to direct a drug to the specific part of the body where it is needed. Thus, although it is often possible to treat a patient with a drug which has the specific effect which is needed, and no other effect on the body, it is still necessary to administer a whole-body dose. On the other hand, if it were possible to direct a drug to the organ, tissue or even cell in need of the treatment, it would often be possible to administer an extremely small total dose, since the drug would concentrate itself where it is needed. The advantage in safety to the patient and economy of drug is obvious.
For some years now, the science of immunology has been attempting to provide such targeted treatments, by conjugating drugs with antibodies which are directed to specific antigens associated with the locations where the drug is needed. Patents and scientific articles concerning such antibody-drug conjugates are now numerous. However, up to the present time, no antibody-drug conjugate is approved for therapeutic use.